U.S. patent application number 13/211869 was filed with the patent office on 2013-02-21 for optical disk playback device with prescan functionality for early detection of surface imperfections.
The applicant listed for this patent is Joseph Michael Freund. Invention is credited to Joseph Michael Freund.
Application Number | 20130044577 13/211869 |
Document ID | / |
Family ID | 47137479 |
Filed Date | 2013-02-21 |
United States Patent
Application |
20130044577 |
Kind Code |
A1 |
Freund; Joseph Michael |
February 21, 2013 |
OPTICAL DISK PLAYBACK DEVICE WITH PRESCAN FUNCTIONALITY FOR EARLY
DETECTION OF SURFACE IMPERFECTIONS
Abstract
An optical disk playback device comprises first and second
lasers, an optical assembly, first and second optical detectors,
and controller circuitry coupled to the optical detectors. The
optical assembly is configured to direct incident light from the
first and second lasers so as to form respective leading and
trailing scanning spots on a surface of an optical disk, and is
further configured to direct corresponding reflected light from the
leading and trailing scanning spots on the surface of the optical
disk to respective ones of the optical detectors. The controller
circuitry is configured to identify a surface imperfection of the
optical disk by processing the reflected light associated with the
leading scanning spot prior to the trailing scanning spot reaching
that surface imperfection.
Inventors: |
Freund; Joseph Michael;
(Fogelsville, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Freund; Joseph Michael |
Fogelsville |
PA |
US |
|
|
Family ID: |
47137479 |
Appl. No.: |
13/211869 |
Filed: |
August 17, 2011 |
Current U.S.
Class: |
369/47.14 ;
G9B/20.009 |
Current CPC
Class: |
G11B 7/0948 20130101;
G11B 7/1275 20130101 |
Class at
Publication: |
369/47.14 ;
G9B/20.009 |
International
Class: |
G11B 20/10 20060101
G11B020/10 |
Claims
1. An optical disk playback device comprising: first and second
lasers; an optical assembly; first and second optical detectors;
and controller circuitry coupled to the optical detectors; the
optical assembly being configured to direct incident light from the
first and second lasers so as to form respective leading and
trailing scanning spots on a surface of an optical disk; the
optical assembly being further configured to direct corresponding
reflected light from the leading and trailing scanning spots on the
surface of the optical disk to respective ones of the optical
detectors; wherein the controller circuitry is configured to
identify a surface imperfection of the optical disk by processing
the reflected light associated with the leading scanning spot prior
to the trailing scanning spot reaching that surface
imperfection.
2. The device of claim 1 wherein the controller circuitry is
further configured to initiate an error recovery algorithm
responsive to the identification of the surface imperfection.
3. The device of claim 1 further comprising first and second
decoders associated with the respective first and second optical
detectors.
4. The device of claim 3 wherein an error recovery algorithm is
initiated in the second decoder responsive to the identification of
the surface imperfection.
5. The device of claim 1 wherein the optical assembly comprises
first optics associated with the first laser and second optics
associated with the second laser.
6. The device of claim 1 wherein the first and second optical
detectors comprise respective first and second arrays of
photo-detectors.
7. The device of claim 1 wherein the first and second lasers are
configured to generate the incident light at substantially the same
wavelength.
8. The device of claim 1 wherein the first and second lasers are
configured to generate the incident light at different
wavelengths.
9. The device of claim 8 wherein the first laser has a wavelength
particularly adapted for reading stored information from a first
type of optical disk and the second laser has a wavelength
particularly adapted for reading stored information from a second
type of optical disk different than the first type of optical
disk.
10. The device of claim 9 wherein the first type of optical disk is
a DVD optical disk and the second type of optical disk is a Blu-ray
optical disk.
11. The device of claim 1 wherein stored information is read from
the optical disk utilizing only the reflected light associated with
the trailing scanning spot.
12. A method comprising: forming leading and trailing scanning
spots on a surface of an optical disk using incident light from
respective first and second lasers; detecting reflected light from
the leading and trailing scanning spots; and identifying a surface
imperfection of the optical disk by processing the reflected light
associated with the leading scanning spot prior to the trailing
scanning spot reaching that surface imperfection.
13. The method of claim 12 further comprising the step of
initiating an error recovery algorithm responsive to the
identification of the surface imperfection.
14. The method of claim 12 further comprising the step of reading
stored information from the optical disk utilizing only the
reflected light associated with the trailing scanning spot.
15. The method of claim 12 further comprising the step of
displaying a message indicating that the surface imperfection has
been identified.
16. The method of claim 12 further comprising the step of providing
a selectable option to at least one of enable and disable
generation of the leading scanning spot.
17. A non-transitory computer-readable storage medium having
embodied therein executable code for performing the steps of the
method of claim 12.
18. An optical disk playback system comprising: first and second
playback mechanisms; the first and second playback mechanisms being
operative to form respective leading and trailing scanning spots on
a surface of the optical disk, and to detect reflected light from
the respective leading and trailing scanning spots; wherein a
surface imperfection of the optical disk is identified by
processing the reflected light associated with the leading scanning
spot prior to the trailing scanning spot reaching that surface
imperfection.
19. The system of claim 18 wherein the first playback mechanism is
particularly adapted for reading stored information from a first
type of optical disk and the second playback mechanism is
particularly adapted for reading stored information from a second
type of optical disk different than the first type of optical
disk.
20. The system of claim 19 wherein the first type of optical disk
is a DVD optical disk and the second type of optical disk is a
Blu-ray optical disk.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to optical disk
playback devices, and more particularly to techniques for improving
the readout performance of such devices in the presence of surface
imperfections on an optical disk.
BACKGROUND OF THE INVENTION
[0002] Standardized optical disk storage formats have recently
evolved from Digital Versatile Disk (DVD) to Blu-ray. A Blu-ray
disk is read using a blue laser having a wavelength of 405
nanometers, significantly shorter than the 650 nanometer red laser
used to read DVDs. Information can therefore be stored at a much
higher density on Blu-ray disks. For example, a single layer
Blu-ray disk can store about 25 Gigabytes (GB) of data, compared to
about 5 GB for a DVD. Higher storage densities can be achieved by
configuring the optical disk to include multiple storage layers, as
is well known.
[0003] Although Blu-ray disks have the advantage of higher storage
density, the use of a shorter wavelength laser for readout can also
be problematic in that it leads to a higher susceptibility to
playback errors arising from scratches, fingerprints, dust
particles, bubbles or other imperfections on or near the disk
surface.
[0004] Depending on the extent of the surface imperfection,
playback by an optical disk playback device can be briefly
interrupted or stopped all together. For small imperfections, the
playback device will typically first attempt to re-read the data
that is in error, and if it cannot re-read the data, the device may
skip ahead and try to read the next data location, continuing this
process until the surface imperfection is finally bypassed and
normal playback resumes. For larger imperfections, the playback
oftentimes freezes completely, as the correction process
implemented in the playback device cannot resolve the situation.
The user may then have to use a "skip" or "fast forward" feature of
the playback device in order to manually step ahead in the playback
sequence, until the surface imperfection is bypassed.
SUMMARY OF THE INVENTION
[0005] An illustrative embodiment of the present invention provides
improved readout performance in an optical disk playback device in
the presence of surface imperfections by implementing prescan
functionality in which a surface imperfection can be detected and
an appropriate error recovery algorithm initiated prior to the read
laser reaching the surface imperfection.
[0006] In one aspect of the invention, an optical disk playback
device comprises first and second lasers, an optical assembly,
first and second optical detectors, and controller circuitry
coupled to the optical detectors. The optical assembly is
configured to direct incident light from the first and second
lasers so as to form respective leading and trailing scanning spots
on a surface of an optical disk, and is further configured to
direct corresponding reflected light from the leading and trailing
scanning spots on the surface of the optical disk to respective
ones of the optical detectors. The controller circuitry is
configured to identify a surface imperfection of the optical disk
by processing the reflected light associated with the leading
scanning spot prior to the trailing scanning spot reaching that
surface imperfection. The controller circuitry may be further
configured to initiate an error correction algorithm or other type
of error recovery algorithm responsive to the identification of the
surface imperfection.
[0007] The first and second lasers may both have substantially the
same wavelength, or may operate at different wavelengths. In an
arrangement of the latter type, the first laser may have a
wavelength particularly adapted for reading stored information from
a first type of optical disk and the second laser may have a
wavelength particularly adapted for reading stored information from
a second type of optical disk different than the first type of
optical disk. For example, the first type of optical disk may be a
DVD optical disk and the second type of optical disk may be a
Blu-ray optical disk, with a DVD laser being used to provide the
leading scanning spot to prescan for surface imperfections and a
Blu-ray laser being used provide the trailing scanning spot to read
stored information from the optical disk.
[0008] Advantageously, the illustrative embodiments provide
significant improvements in readout performance of a Blu-ray
optical disk or other type of optical disk in the presence of
surface imperfections on that disk. The surface imperfections are
detected early using a leading scanning spot, and can therefore be
automatically addressed in a manner that is entirely transparent to
the viewer, thereby avoiding the need for manual intervention. By
way of example, this significant improvement over conventional
practice can be achieved in a playback device which already
comprises both DVD and Blu-ray readout capability, by utilizing the
DVD laser to generate the leading scanning spot that detects
surface imperfections prior to readout by the Blu-ray laser. In
such an arrangement, the enhanced readout performance may be
provided without the need for any significant additional optics or
readout hardware.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a block diagram of an optical disk playback system
that incorporates prescan functionality for early detection of
surface imperfections in an illustrative embodiment of the
invention.
[0010] FIG. 2 shows a more detailed view of a portion of the FIG. 1
system, illustrating the formation of leading and trailing scanning
spots by an optical pickup unit on a surface of an optical
disk.
[0011] FIG. 3 is a flow diagram showing one mode of operation of
the FIG. 1 system.
DETAILED DESCRIPTION OF THE INVENTION
[0012] The invention will be illustrated herein in conjunction with
an exemplary optical disk playback system that advantageously
incorporates prescan functionality for early detection of surface
imperfections. It should be understood, however, that the invention
is not limited to the particular systems and techniques shown and
described. The present invention is more generally applicable to
any optical disk playback system in which improved readout
performance is desired, and may be implemented using components
other than those specifically shown and described in conjunction
with the illustrative embodiments.
[0013] FIG. 1 shows an optical disk playback system 100 in
accordance with an illustrative embodiment of the invention. The
playback system 100 in this embodiment more specifically comprises
an optical pickup unit 102 that reads stored information from an
optical disk 104. The optical pickup unit may also be configured to
write information to a recordable optical disk, although such
functionality is not a requirement of the present invention. In a
typical configuration, the optical disk 104 is inserted in a disk
drive which controls the rotation of the disk as well as the
positioning of the optical pickup unit 102 relative to grooves of
the disk. The drive mechanisms and associated electronics for
controlling rotation of the optical disk 104 and positioning of the
optical pickup unit 102 are omitted from the figure for clarity and
simplicity of illustration, but may be assumed to be implemented in
a conventional manner.
[0014] The optical pickup unit 102 in the present embodiment
comprises lasers 110, optics 112 and optical detectors 114. It will
be assumed without limitation that there are at least first and
second lasers and at least first and second optical detectors,
although other numbers of lasers and detectors can be used in other
embodiments. The first and second lasers may both have
substantially the same wavelength, or may operate at different
wavelengths. In an arrangement of the latter type, the first laser
may have a wavelength particularly adapted for reading stored
information from a first type of optical disk and the second laser
may have a wavelength particularly adapted for reading stored
information from a second type of optical disk different than the
first type of optical disk. For example, the first type of optical
disk may be a DVD optical disk and the second type of optical disk
may be a Blu-ray optical disk. Multiple layer optical disks of
these and other formats may also be used.
[0015] The optics 112 may be viewed as an example of what is more
generally referred to herein as an "optical assembly." The term
"optical assembly" as used herein is intended to be broadly
construed, and may comprise any arrangement of optical elements
used to direct light to and from the optical disk 104, and may also
include associated structural, mechanical or electrical elements.
An optical assembly may comprise entirely separate sets of optics
associated with the respective first and second lasers, or may
utilize at least a subset of its optical elements to process light
from both the first and second lasers. It should therefore be
appreciated that the present invention does not require any
particular arrangement of optics for directing light to and from
the optical disk, even though a more detailed example of such
optics will be described in conjunction with FIG. 2.
[0016] The optical pickup unit 102 is coupled to a processor 120
which controls the operation of the optical pickup unit and
processes signals supplied by and delivered to that unit. The
processor 120 may comprise, by way of example, a microprocessor, a
digital signal processor (DSP), an application-specific integrated
circuit (ASIC), a field-programmable gate array (FPGA), or other
integrated circuit device, as well as portions or combinations of
such devices. The processor 120 may be viewed as an example of what
is more generally referred to herein as "controller circuitry."
Such controller circuitry, although shown as separate from the
optical pickup unit 102 in the present embodiment, may be
implemented at least in part within the optical pickup unit in
other embodiments. As the term is used herein, "controller
circuitry" may therefore encompass, again by way of illustrative
example and without limitation, disk drive electronics, signal
processing electronics, and associated processing and memory
circuitry, as well as one or more related electromechanical
elements utilized to control positioning of the optical pickup unit
102 relative to the surface of the optical disk 104.
[0017] The controller circuitry as described above is assumed to be
coupled to outputs of the optical detectors 114 and to receive
respective detected signals therefrom for further processing
associated with prescan and readout, and may additionally be
coupled to other elements of the optical pickup unit, such as
control inputs of the lasers 110.
[0018] Also associated with the processor 120 in the optical
playback system 100 is memory 122 and decoders 124. The memory 122
stores executable code that may be executed by processor 120 in
implementing at least a portion of the prescan and readout
functionality. The memory 122 may comprise electronic memory such
as random access memory (RAM) or read-only memory (ROM), in any
combination, and is an example of what is more generally referred
to herein as a "computer-readable storage medium."
[0019] The decoders 124 may comprise, for example, separate DVD and
Blu-ray decoders in an embodiment designed to support playback of
both DVD and Blu-ray optical disks. Such decoders will generally
include MPEG-2 decoding functionality, and may be associated with
respective ones of the first and second optical detectors 114. In
other embodiments, a single decoder may be used to support multiple
optical disk formats.
[0020] Information signals read out from the optical disk 104 are
processed by decoders 124 to generate video signals suitable for
presentation on display device 125. The display device may
comprise, for example, a television, computer, mobile telephone, or
any other processing device having an ability to display video or
other information read out from the optical disk 104 via the
optical pickup unit 102.
[0021] The system elements 102, 120, 122 and 124 may comprise
elements of an otherwise conventional optical disk playback device,
such as a Blu-ray player that is also backwards compatible with the
DVD format. One or more such elements may be implemented in a
processing device such as the television, computer, mobile
telephone, or other processing device that provides the display
device 125.
[0022] System elements such as optical detectors 114, processor
120, memory 122 and decoders 124 may be implemented at least in
part in the form of one or more integrated circuits, such as an
otherwise conventional system-on-chip (SOC) integrated circuit
designed for use in an optical disk player or other optical disk
playback device and suitably modified to support prescan
functionality as disclosed herein.
[0023] In an integrated circuit implementation of the invention,
multiple integrated circuit dies are typically formed in a repeated
pattern on a surface of a wafer. Each such die may include a device
as described herein, and may include other structures or circuits.
The dies are cut or diced from the wafer, then packaged as
integrated circuits. One skilled in the art would know how to dice
wafers and package dies to produce packaged integrated circuits.
Integrated circuits so manufactured are considered part of this
invention.
[0024] As noted above, a problem that can arise in reading stored
information from an optical disk such as optical disk 104 is
susceptibility to playback errors arising from scratches,
fingerprints, dust particles, bubbles or other imperfections on or
near the disk surface. This is particularly true for optical disks
having high-density storage formats such as Blu-ray in which the
readout is performed using a short wavelength blue laser.
[0025] The present embodiment overcomes this significant problem of
the prior art at least in part by configuring an optical assembly
comprising optics 112 to direct incident light from the first and
second lasers 110 so as to form respective leading and trailing
scanning spots on a surface of the optical disk 104, and to direct
corresponding reflected light from the leading and trailing
scanning spots on the surface of the optical disk 104 to respective
ones of the optical detectors 114. The processor 120 or other
controller circuitry of the system 100 is configured to identify a
surface imperfection of the optical disk 104 by processing the
reflected light associated with the leading scanning spot prior to
the trailing scanning spot reaching that surface imperfection. The
controller circuitry may be further configured to initiate an error
correction algorithm or other type of error recovery algorithm
responsive to the identification of the surface imperfection. Such
an error recovery algorithm may be implemented, by way of example,
within the processor 120, or within a given one of the decoders
124.
[0026] As noted above, the first and second lasers may both have
substantially the same wavelength, or may operate at different
wavelengths. In an embodiment in which the first laser is a DVD
laser configured for reading a DVD optical disk and the second
laser is a Blu-ray laser configured for reading a Blu-ray disk, the
DVD laser may be used to provide the leading scanning spot to
prescan for surface imperfections and the Blu-ray laser may be used
to provide the trailing scanning spot to read stored information
from the optical disk. More generally, in a playback device in
which two different lasers are configured to read two different
types of optical disks, the laser configured to read one type of
disk serves to form a leading scanning spot when the other type of
disk is being read using a trailing scanning spot formed by the
other laser, and vice-versa.
[0027] The optical disk playback system 100 as illustrated in FIG.
1 may include other elements in addition to or in place of those
specifically shown, including one or more elements of a type
commonly found in a conventional implementation of such a system.
These and other conventional elements, being well understood by
those skilled in the art, are not described in detail herein. It
should therefore be understood that the particular arrangement of
elements shown in FIG. 1 is presented by way of illustrative
example only. Accordingly, those skilled in the art will recognize
that a wide variety of other optical disk playback system
configurations may be used in implementing the invention.
[0028] FIG. 2 shows a more detailed view of the optical pickup unit
102 and illustrates the formation of leading and trailing scanning
spots on a surface of the optical disk 104. In this figure, the
first and second lasers are more specifically identified as lasers
110-1 and 110-2, respectively, and as noted above may comprise
lasers configured for reading of respective DVD and Blu-ray optical
disks. The lasers 110-1 and 110-1 may therefore comprise a red
laser having a wavelength of about 650 nanometers and a blue laser
having a wavelength of about 405 nanometers, respectively. The
first and second optical detectors are more specifically identified
as respective first and second arrays of photo-detectors 110-1 and
114-2.
[0029] The optics 112 in this embodiment more specifically comprise
optical elements 202, 204, 206 and 208 which are arranged for
directing light from the lasers 110 to the optical disk 104 and
from the optical disk 104 to the arrays of photo-detectors 110-1
and 114-2. More specifically, the optics 112 direct the incident
light from the first laser 110-1 to form leading scanning spot 210
and direct the corresponding reflected light from the leading
scanning spot 210 to the first photo-detector array 114-1.
Similarly, the optics 112 direct the incident light from the second
laser 110-2 to form trailing scanning spot 212 and direct the
corresponding reflected light from the trailing scanning spot 212
to the second photo-detector array 114-2. The leading scanning spot
210 is used to prescan for surface imperfections, and the trailing
scanning spot is used to read stored information from the optical
disk 104.
[0030] It should be noted that the scanning spots 210 and 212 are
shown in the figure as being above the surface of the optical disk
104, but this is only for clarity of illustration. One skilled in
the art will appreciate that the scanning spots in practice will
illuminate the actual surface of the optical disk, and are
therefore referred to herein as being formed on the surface of the
optical disk using light from the lasers 110-1 and 110-2.
[0031] In operation, the leading scanning spot 210 scans the groove
of the rotating optical disk 104 just ahead of the trailing
scanning spot 212. The reflected light from the leading scanning
spot 210 is detected in the first photo-detector array 114-1 and
the resulting detected signal is used in the above-noted controller
circuitry to identify a surface imperfection of the optical disk
104. The reflected light from the trailing scanning spot 212 is
detected in the second photo-detector array 114-2 and the resulting
detected signal provides readout of stored information for
presentation on the display 125. The leading scanning spot 210 is
arranged sufficiently in advance of the trailing scanning spot 212
to permit a surface imperfection at a given location to be
identified and an appropriate error recovery algorithm to be
triggered prior to the trailing scanning spot reaching the location
of that surface imperfection.
[0032] The optical elements 202, 204, 206 and 208 as shown
illustratively comprise optical elements that pass light arriving
one direction and reflect light arriving from the opposite
direction. For example, optical element 206 directs incident light
from laser 110-1 to the surface of the optical disk 104 and directs
the corresponding reflected light from the surface of optical disk
104 to the photo-detector array 114-1. Similarly, optical element
208 directs incident light from laser 110-2 to the surface of the
optical disk 104 and directs the corresponding reflected light from
the surface of optical disk 104 to the photo-detector array 114-2.
However, it is to be understood that a wide variety of alternative
arrangements of optical elements may be used to direct incident and
reflected light in the optical pickup unit 102. Such arrangements
of optical elements are all intended to be encompassed by the
general term "optical assembly" as used herein.
[0033] Referring now to FIG. 3, a flow diagram is shown of a
process implemented in the optical playback system 100. The process
is performed by the system 100 under the control of processor 120
in an operating mode involving prescanning of the optical disk 104
for surface imperfections. The process includes steps 300 through
310. One or more of the steps may be carried out responsive to
execution of corresponding software code in the processor 120.
[0034] In step 300, optical disk playback is initiated with the
prescan mode enabled. This may involve, for example, a user
inserting the optical disk 104 in a disk drive and manipulating
appropriate playback device control inputs to select the prescan
mode. Thus, a playback device configured in accordance with the
invention may provide a user with selectable options to enable or
disable generation of the leading scanning spot 210 and thereby to
enable or disable the prescan functionality of the playback device.
Such options may be provided through suitable modification of an
otherwise conventional user interface of the playback device.
Alternatively, the playback device may be configured such that the
prescan mode of playback is automatically enabled any time playback
is selected.
[0035] In step 302, both the first and second lasers 110-1 and
110-1 and their corresponding detectors 110-1 and 114-2 are turned
on.
[0036] In step 304, the leading and trailing scanning spots 210 and
212 are formed on the surface of the optical disk 104 using
incident light from the respective first and second lasers 110-1
and 110-2. Although shown as a separate step in the figure, step
304 may be carried out by simply turning on the lasers and
detectors in step 302. The scanning spot formation step 304 may
additionally or alternatively involve some movement or other
adjustment of the positioning of one or more elements of the optics
112, as well as adjusting the speed of rotation of the optical disk
104 until it reaches an appropriate readout speed.
[0037] In step 306, reflected light is detected from the leading
and trailing scanning spots 210 and 212 in the respective detectors
110-1 and 114-2. The process scans for surface imperfections using
the leading scanning spot 210 while simultaneously reading stored
information from the disk using the trailing scanning spot 212. The
readout of stored information using the trailing scanning spot 212
may be performed in a well-known conventional manner, and is
therefore not described in detail herein.
[0038] In step 308, a determination is made based on the reflected
light from the leading scanning spot 210 whether or not an
imperfection is present in the corresponding location on or near
the surface of the optical disk 104. Such imperfections may
include, for example, scratches, fingerprints, dust particles,
bubbles, dents, uneven surface areas, manufacturing defects,
recording defects or other imperfections on or near the disk
surface, or portions thereof. It should therefore be appreciated
that the term "surface imperfections" as used herein is intended to
be broadly construed, so as to encompass, for example, defects on
or near the surface that may arise during manufacturing of the
optical disk or in conjunction with recording of information on the
optical disk, as well as those imperfections that may arise by
improper handling of the optical disk. Such surface imperfections
may therefore include imperfections that extend from the surface
into an area below the surface, or are entirely below the surface
but are nonetheless detectable from the surface using the leading
scanning spot 210.
[0039] The detection of particular surface imperfections in the
present embodiment involves processing of a detected signal from
the detector 114-1 to determine if the detected signal indicates
the presence of a surface imperfection. This may involve, for
example, matching one or more characteristics of the detected
signal to corresponding known characteristics of particular types
of surface imperfections. Those skilled in the art will recognize
that pattern matching algorithms may be used for this purpose.
[0040] If step 308 indicates the presence of a surface imperfection
based on the reflected light from the leading scanning spot 210,
the process moves to step 310, and otherwise returns to step 306 to
continue scanning for surface imperfections using the leading
scanning spot 210 while simultaneously reading stored information
from the disk using the trailing scanning spot 212. If a surface
imperfection of sufficient magnitude is identified, a message to
that effect may be presented on the display 125, such the user will
understand that the output video may temporarily altered in
accordance with the processing operations of an error recovery
algorithm. For example, such a message may be generated and
displayed upon detection of the previously-noted larger surface
imperfection that otherwise under conventional practice might cause
the playback process to be completely frozen.
[0041] In step 310, the error recovery algorithm is initiated
responsive to detection of the surface imperfection in step 308.
The error recovery algorithm is initiated for a given surface
imperfection location prior to the trailing scanning spot reaching
that location, which allows the system additional flexibility in
addressing the imperfection. For example, for a particular detected
imperfection, the error recovery algorithm that is initiated may
direct the decoder to continue to display a previous video output
frame for a designated period of time before resuming playback
using stored information read from the optical disk. This avoids
the above-described conventional problem of playback freezing
completely, and does not require any user intervention, such as
using a "skip" or "fast forward" feature of the playback device in
order to manually step ahead in the playback sequence until the
surface imperfection is bypassed. An error recovery algorithm of
the type referred to herein will generally allow the imperfection
to be bypassed, for example, with the Blu-ray playback decoder
supplying appropriate image data so as to minimize visual
disturbance to the viewing experience.
[0042] The particular process steps and their ordering as
illustrated in FIG. 3 may be varied in other embodiments. For
example, steps that are shown as being performed sequentially in
FIG. 3 may instead be performed at least in part in parallel with
one another. Numerous alternative or additional steps may be
used.
[0043] It was indicated previously that at least a portion of the
system 100 may be embodied in an otherwise conventional optical
disk playback device, such as a Blu-ray player that is also
backward compatible with the DVD format. In an arrangement of this
type, the optical disk player will generally comprise two separate
playback mechanisms, one for playing back DVDs and the other for
playing back Blu-ray disks. The DVD laser of the DVD playback
mechanism can generally be turned on and operated entirely
independently of the Blu-ray laser of the Blu-ray playback
mechanism, and vice-versa. The DVD and Blu-ray lasers can therefore
both be turned on together in order to form respective leading and
trailing scanning spots on a surface of an optical disk, such that
reflected light can be detected from the respective leading and
trailing scanning spots. As in one or more of the
previously-described embodiments, a surface imperfection of the
optical disk may be advantageously detected or otherwise identified
by processing the reflected light associated with the leading
scanning spot prior to the trailing scanning spot reaching that
surface imperfection.
[0044] In one or more of the illustrative embodiments, surface
imperfections are detected early using a leading scanning spot, and
can therefore be automatically addressed in a manner that is
entirely transparent to the viewer, thereby avoiding the need for
manual intervention. By way of example, this significant
improvement over conventional practice can be achieved in the
above-noted otherwise conventional playback device which already
comprises both DVD and Blu-ray readout capability, by utilizing the
DVD laser to generate the leading scanning spot that detects
surface imperfections prior to readout by the Blu-ray laser. In
such an arrangement, the enhanced readout performance may be
provided without the need for any significant additional optics or
readout hardware.
[0045] Again, it should be emphasized that the above-described
embodiments of the invention are intended to be illustrative only.
For example, other embodiments can use different types and
arrangements of lasers, optics, detectors and controller circuitry.
Also, different types of surface imperfection detection techniques
and associated error recovery algorithms may be used. As a more
particular example, an embodiment may be configured which utilizes
more than two lasers, and associated optics and detectors, with one
of the lasers and its optics and corresponding detector being
optimized to detect surface imperfections on multiple optical disk
types, and the other lasers and their optics and corresponding
detectors being optimized for readout of stored data from
respective different optical disk formats, such as Blu-ray and DVD
formats. These and numerous other alternative embodiments within
the scope of the following claims will be apparent to those skilled
in the art.
* * * * *